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  <title>Adjusts the levels of an image</title>

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</div><hr /><div id="gmagick.levelimage" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">Gmagick::levelimage</h1>
  <p class="verinfo">(PECL gmagick &gt;= Unknown)</p><p class="refpurpose"><span class="refname">Gmagick::levelimage</span> &mdash; <span class="dc-title">Adjusts the levels of an image</span></p>

 </div>

 <div class="refsect1 description" id="refsect1-gmagick.levelimage-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="modifier">public</span> <span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <span class="methodname"><strong>Gmagick::levelimage</strong></span>
    ( <span class="methodparam"><span class="type">float</span> <code class="parameter">$blackPoint</code></span>
   , <span class="methodparam"><span class="type">float</span> <code class="parameter">$gamma</code></span>
   , <span class="methodparam"><span class="type">float</span> <code class="parameter">$whitePoint</code></span>
   [, <span class="methodparam"><span class="type">int</span> <code class="parameter">$channel</code><span class="initializer"> = Gmagick::CHANNEL_DEFAULT</span></span>
  ] )</div>

  <p class="para rdfs-comment">
   Adjusts the levels of an image by scaling the colors falling between specified white and black
 points to the full available quantum range. The parameters provided represent the black, mid, and 
  white points. The black point specifies the darkest color in the image. Colors darker than the black
 point are set to zero. Mid point specifies a gamma correction to apply to the image. White point
 specifies the lightest color in the image. Colors brighter than the white point are set to the
 maximum quantum value. 
  </p>

   

 </div>


 <div class="refsect1 parameters" id="refsect1-gmagick.levelimage-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<em><code class="parameter">blackPoint</code></em></dt>

     <dd>

      <p class="para">
       The image black point 
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">gamma</code></em></dt>

     <dd>

      <p class="para">
       The gamma value 
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">whitePoint</code></em></dt>

     <dd>

      <p class="para">
       The image white point 
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">channel</code></em></dt>

     <dd>

      <p class="para">
       Provide any channel constant that is valid for your channel mode. 
To apply to more than one channel, combine channeltype constants using bitwise
 operators. Refer to this list of <a href="gmagick.constants.html#gmagick.constants.channel" class="link">channel constants</a>.
      </p>
     </dd>

    
   </dl>

  </p>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-gmagick.levelimage-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   Gmagick object with image levelled.
  </p>
 </div>

 <div class="refsect1 errors" id="refsect1-gmagick.levelimage-errors">
  <h3 class="title">错误／异常</h3>
  <p class="para">
   错误时抛出
<strong class="classname">GmagickException</strong>。
  </p>
 </div>

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